Lens-blocking apparatus.



GOTLIEB H. FLAIOy OF ROCHESTER, NEW YORK, ASSIGNOR TO IBAUSCH 6c LOMB OPTIC-L COMPANY, F ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

f LENS-BLOCKING APPARATUS.

Specification of Letters Patent.

Patented Nov. 12, 1918.

To all whom it may concern.'

Be it known that I, GrorLin-H. FLAI), citizen of the United States, residing),` at Rochester, in the county of Monroe, State of New York, have invented certain new and useful Improvements' in Lens-Blocking Apparatus; and l do declare the following to be a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming a part of this specification, and to the characters of reference marked thereon. y

rThis invention relates more particularly to apparatus for blocking lens .blanks preparatory to `grinding' and polishing' them,

and has for its main object to providea lensy blank blocking apparatus which renders unnecessary expensive skilled labor for forme ing' accurate impressions of those faces of the lens blanks secured to the lens block prior to grinding their opposite faces to either plano or curved forms, and also to assure unusual durability ofthe blocking tools and to provide for their repair or replacement at minimum expense, thereby lessening the cost of the finished lenses While also assuring' that curved lenses of any form .so blocked shall be free from refractive aberration of, astigmatism In the drawings:

Figure. 1 is a vertical section of the separated elements used in one embodiment of4 this invention as employed for blocking,` a group of lens blanks upon each of which a plano face is to be ground. Fig. '2 is a face view of the templet shown in 1.. Fig. 3 is a perspective view of one o. the

lens spot patterns. Fig. l is a cross section showing the first step of molding the plastic material upon the spots andtemplet to the form of those' surfaces ofthe various lens blanks to later be secured to a pitch layer on the block.- 5 is a cross section illustrating the block and the adhering impressed and hardened plastic material and shown separated from the spots and templet which remain on the underlying surface plate. Fig. G is a top plan view of the plano block showing the impressions of the spots made in the plastic material thereon, and

r withbut ten lens blanks on a like number of thesspot impressions. Fig. 7 `is a sectional elevation showing the plano lens block and the entire group of applied lensesas adlu'ted for operation of a superimposed plano grinding tool. Fig. 8 is a cross section illustrating the taking' of impressions of spots held on a concave surface plate.. 'Fig'. 9 is a 'cross section illustrating the taking of imindicates a fiat templet w ich in use is laidl upon the plate-1, or upon'the grinding lap itself, and has a plurality of openingsin which are firstplaced a series of quiteclosely fitting patterns or spots 4, shownA with one 'lower plane-face and shaped at their upper faces to correspond with theY contour of the finished or unfinished plano or 'convex or'.

concave faces of a series of lens blanks shown in Figs. 6 and 7 of the drawings. The edges or peripheral faces of the spots 4 which iit within the templet openings 3 -are preferably somewhat 'thicker than the templet 2, as more clearly shown in Figs. 1 and '5, to later provide for `both a face and an edge hold for the lens blanks in the bed 6, composed of' pitch or other adhesive compound adhering to the face of the lens blockl 7; the lens blanks 5 being applied .in the In practising one embodiment of this in-` molded impressions formed by the spots 4.

'ventiomthetemplet 2 is first laid upon the surface plate 1, and the lens patterns or spots 4. are placed in the templet openings 3 and rest on the plate. Any suitable powder facing is now dusted over the templet and the spots, and a layer 6 of pitch then is applied over the facing covered templet and spots. The leus block 7, usually made of iron, to which the pitch will tenaciously adhere, is now placed upon the soft pitch layer 6 upon which the block ismanually or otherwise pressed with suflicient force to mold the pitch into impressions or forms 8 corresponding to the contour of the upper faces of the spots 4, `and the intervening flat and slightly lower portions of the templet 2,'as

molded pitch layer 6 has set or hardened suiliciently, the lensblock 7 with the adher-i 105 ing molded and hardened pitch, is lifted from the templet 2 and spots 4 which remain f 'upon the surface plate 1, as shownin Fig. 5.

The block T. is now inverted to bring itsV adhering molded pitch layer 6 uppermost, and the lens blanks which are to be ground, after being sutliciently heated so as to soften the surface of the impressions in the pitch are laid with their proper faces downward into the Correspondingly formed innnessions El, and under light manual pressure will adhere firmly to the pitch on their faces and at their edges or corn-ers, thus giving the blanks both a face hold and an edge hold. rilhe pitch which quickly hardens, as the heated blanks cool. securely holds them in true. position on the lens block 'T relatively to the optical axes of any or all `curved faces of the blanks which may have been first ground or finished on their obverse faces.

'.len of the lens blanks so held in the pith lfthe applied lens blanks have au edge hold in the pitch impressions S.

Fig. T :if the drawings shows the lens blank carrying block 7 held to a supporting part 9 of a lens grinding machine having a plano grinding tool or lap 10 operated by a cranked pin 11 rotating with av shaft 12 to which the pin is fixed, for grinding` in true planes the upper faces of all the lens-blanks 5 fastened to the block 7. It will beseen that the use of the templet 2 with the spots 4. assures the projection of the unground faces of the lens blanks 5 well above the outer face of the pitch layer (i, or for a distance about cqualing the thickness of the lemplet 2, and consefpiently there can be no interference by the pitch layer with the following lens grinding operation which may be begun almost immediately after the lens blanks .3 are manually applied to the pitch layer (l. as little or no routing or cuttingr away of surplus pitch from around the edges of the lens blanks is necessary. in the illustrated examples some of the finished lenses when removed from the pitch layer 6 would f have double-plano form. otners would have,

plano-convex form. and still others would have plano-coiuave form. but the entire groin) of lenses may have similar form. and the ground lenses of any form may have any desired thickness` and the curved faces of the lenses may be struck on arcs having longer or shorter radii as may be required to produce any special refractive qualities in the lenses.

This invention is especially well adapted presses" an interposed pitch layer 22,

In Fig. 8, the surface plate 13, corresponding to the grinding lap, is concave and is curved on an are which corresponds. with the desired degree of convexity to be given the reverse faces'of the lens blanks secured to the convex block le prior to the iinal grindingand polishing operations. The templet 15 is here eonvexed to tit closely upon the concave plate 13, and the spots 16, preferably having lowerfaces fitting closely upon the plate are placed thereon within the openings of the preferably thinner teinplet 15. The spots and templet now are dusted with a powder facing and then are covered by a soft pitch layer 17 upon which the convex blockfl is pressed to form in the pitch impressions of the upper faces and portions of the edges of the spots, and after the pitch has hardened the block 14, with thev adhering impressed or molded pitch layer 17, is lifted from the templet and spots and inverted and the heated lens blanks are pressed with their first finished obverse faces upon the proper spot impressions and adhere thereto. The lens blank holding block let is now placed upon a grinding ma chine element such as 9, and a suitable concave grinding lap is employed to reduce the reverse and now uppermost faces of the blanks tothe desired convex-form. In Fig. 9 of the drawings the surface plate 18 is convex, and the templet 19 and the lower faces of the preferably thicker spots 20 conform thereto, and 'the concave lens block 21 p which later receives and adhesively supports the lens blanks in the spot impressions in readiness for grinding the blanks to concavel form at their projecting reverse rfaces'by a suitable convex grinding tool. In both adaptations of the invention shown in Figs. 8 and 9, the routingr of surplus pitch from around the lens blanks attached to the lens block is avoided or minimized by using` the curved icmplet. substantially as*` when the above described plano surface plate and templet and leus` block are eiliployed.

The linished faces of the spots 1G or Q0, which correspond in form with the first lin- -ished obverse faces ol the lens blanks are truly fornud relatively lo lhe opposite faces ol the spots which rest ou the surface plates. so that when t-lnl spots are. laid upon the corresponding surface plate 13 or 1S. they will make such truly centered impressions i-n the pitch layer 12T or' 22, when pressed by thelens block 14 or 21, that when the lens blanks already finished on their vfirst or obverse faces are applied to the spot impressions in the pitch layer on the lens block. the optical centers of the irst finished'obverse `bla-nk faces will be in exact valinement with the optical centers of the later finished reverse facesofthe lenses which are ground by aytool,

or lap,vhaving substantially'the same curvature as the surface plate 13 or 18, and consequentlyA the finished lenses having curved aberration or astigmatism.

I opposite faces will be free from refractive A marked advantage of this invention lies in the facility-With Which the lens blocking tools, especially the lsurface plate, corresponding to the grinding lap, and the templet, are first accurately made and remain in working order. By using this iiivention the surface plate may be quickly and accurately machined either plane or curved, or the grinding lap itselfr may be' used on a support for the templet and spots. The templet may easily and cheaply be made' from rolled sheet metal of standard thickness and later drilled to form the spot receiving openings 3 of proper size, and then curving those templetsvvhichO are tov conform to convex or concave surface plates. Furthermore, should the Aoriginally true face of any Asurface plate become Worn at placesA by long use, the 'entire face ofthe plate may again lbelcheaply machined to pro.- duce another uniformly true surface, and

one surface plate Vmay beV resurfaced `several times and thus may be serviceable for a long period. f Having thus described my invention, what l claim and desire to secure by Letters Pat Yent of the United States is:

1. A lens blocking apparatus comprising a' surface plate, and a templet adaptedto overlie the surface plate and having a plurality of openings adapted to receive and position a plurality of lens spot patterns upon the surface plate preparatory to taking their impressions in adhesive material. on a lens block.

2. A lens blocking apparatus comprising a surface plate; a templet adapted to over lie the surface plate and having a plurality ofr openings, and afplurality of .lens spot patterns each having a thickness greater than the thickness of the templet and adapted to seat themselves steadily upon the sur-l face plate Within said openings preparatory to taking their impressions in plastic material on -a lensblock. 3. ln a lens blocking apparatus, the com# bination cfa surface plate having a surface curved to correspond to the surface of a grinding-lap, a templet curved to correspond tov the curvature of the yplate and having a plurality of spaced openings, lens spot patterns in said openingsand projecting above the surface of the templet, a lens block, and means for taking impressions of the lens spot patterns on the lens block.

i. 'In a lens blocking apparatus, the com- .bination of a surface plate having a surface curved to correspond to the surface of av Gorman H. FLAD.

Copies of this patent may' be obtained for five cents eacln'byaddressing the "Commissioner of Patentu.

Washington, D. G. 

